As illustrated in FIGS. 1 and 2, separator plates 100, to which thin reaction membranes 200 of a fuel cell are secured, are generally provided on opposite sides thereof with manifold holes 110.
Among these, an air supply manifold 111 located at one side serves to supply oxygen and hydrogen, which serve as fuels of the fuel cell, and an air discharge manifold 112 located at the other side serves to discharge air and water remaining after a reaction.
The thin reaction membrane 200 consists of a gas diffusion layer (GDL) and a membrane electrode assembly (MEA). The separator plates 100 serve to secure the thin reaction membranes 200, and are configured to form flow-path channels 320 through which fuel and cooling water flow. The separator plates 100 take the form of a stack of anode separator plates 100b and cathode separator plates 100a, alternately stacked one above another.
The flow-path channels 320 are spaces defined between flow-path lands 310 formed on the surface of the separator plate 100. The flow-path lands 310 take the form of protrusions, and serve not only as a passage through which electricity generated by a chemical reaction moves, but also to form the outer rims of the flow-path channels 320.
As illustrated in FIGS. 4A and 4B in greater detail, an entrance/exit structure is located between the manifold holes 110 and the flow-path channels 320 so as to enable communication of the two with each other. The fuel supplied through the manifold holes 110 is introduced into the flow-path channels 320 through a plurality of communication holes 140, which are formed in the separator plate 100.
Dual gaskets 120 and 130 include respective blocking portions 121 and 131, which are installed between the manifold holes 110 and the communication holes 140 formed in the separator plate 100, and respective separating portions 122 and 132, which are installed between the communication holes 140. The gaskets 120 and 130 serve as a support body between the separator plates 100 stacked one above another.
To assist the understanding of the entrance/exit structure described above, FIG. 2 illustrates a plan sectional view of the fuel cell. The anode separator plate 100b and the cathode separator plate 100a are arranged close to each other with the thin reaction membrane 200 interposed therebetween. The fuel, introduced through the air supply manifold 111, passes through the passage, which is supported by the gaskets 120 and 130 and support members 150, and the communication holes 140, and is then introduced into the flow-path channels 320. Conversely, air and water, discharged from the flow-path channels 320, pass through the communication holes 140, and are then discharged through the air discharge manifold 112.
In the entrance/exit structure, parallel boundary portions are present between the gaskets 120 and 130 and the flow-path channels 320. This is because the separator plate 100 requires space for the installation of molds in order to provide the separator plate 100, which is formed of a metal, with the gaskets via integral injection molding. To this end, flat portions having a length of about 1 mm or more need to be formed between the flow-path channels 320 and the ends of the separating portions 122 and 132 of the gaskets 120 and 130.
FIG. 3 illustrates an image of neutrons inside the fuel cell that is operating. The neutrons appear brighter as the concentration of water molecules increases and appear darker as the concentration of water molecules decreases.
As illustrated in FIG. 3, the reason why the amount of water generated by a chemical reaction increases with decreasing distance from the left side (the entrance) to the right side (the exit) is that the amount of water generated by the reaction of fuel increases. In addition, water is collected into and pools in the lower end due to gravity. As can be appreciated from the figure of an exit hole represented by the bright color in the lower right-hand corner of FIG. 3, water may be excessively accumulated and may not be properly discharged through the exit hole, and consequently air may not be properly discharged due to the accumulated water, thus causing problematic electricity generation.
When the water is not properly discharged, the supply of electric power may become problematic and the thin reaction membrane may be exposed to water for a long time, leading to a possible deterioration in performance.
In the related art, the flat portions described above are arranged above one another in the form of a straight line, which causes water to easily fall down and collect at the exit hole, located at the lower end of the structure.
This problem occurs in the entrance portion as well as in the exit portion of the fuel cell described above. Humidified fuel is generally supplied in order to improve the performance of the fuel cell. At this time, condensed water may be introduced into the reaction plane, and the condensed water introduced through the manifold may be collected into a lower flow path through the flat portions between the flow-path channels and the gaskets.
Therefore, there is a demand for a fuel cell having an entrance/exit structure capable of preventing water from collecting at an exit hole located at a lower end of the structure.